The present invention relates to a gas sensor, such as a hydrogen gas sensor for measuring the hydrogen concentration of a fuel gas used in a fuel cell.
With a growing awareness of global-scale environmental deterioration in the recent years, fuel cells have been intensively studied as clean and efficient power sources. Among various fuel cells, a polymer electrolyte fuel cell (PEFC) is expected to be suitable for car and home use owing to its advantageous characteristics, e.g., low-temperature operability and high output density. In the fuel cell, a reformed gas (obtained from natural gas, methanol or the like) is commonly used as a fuel gas. In order to further improve the efficiency and other performance figures of the fuel cell, there is a need to provide a gas sensor capable of directly measuring the concentration of hydrogen in the reformed gas.
Japanese Laid-Open Patent Publication No. 2001-215214 discloses one type of hydrogen gas sensor 1000, which includes a sensor element provided with a proton-conductive layer 1010 and first and second electrodes 1020 and 1030, a pair of support plates 1050 and 1060 and a sensor mount 1070 as shown in FIG. 17. The proton-conductive layer 1010 is made of a polymer electrolyte. The first and second electrodes 1020 and 1030 are arranged on opposite surfaces of the proton-conductive layer 1010. The support plates 1050 and 1060 support therebetween the sensor element and are held at base end sides thereof to the sensor mount 1070. The hydrogen gas sensor 1000 is fixed to a pipe 1080 to measure the concentration of hydrogen in a gas under measurement flowing through the pipe 1080.